The authors develop an analytical model of satellite communication networks using time-division multiple-access (TDMA) and multiple-carrier TDMA (MC-TDMA) systems to support circuit-switched traffic. The model defines the functions required to implement fixed assignments (FAs), variable destinations (VDs), and demand assignments (DAs). The authors describe a general system model for the various allocation schemes and traffic activity. They define analytical expressions for the blocking and freeze-out probabilities. This is followed by the derivation of the satellite capacity requirements at a specified performance level for FA, VD, and DA systems with and without digital speech interpolation. The analysis of disjoint pools and combined pools in DA systems is presented and attention is given to MC-TDMA with limited connectivity demand assignment. Expressions for the required satellite capacity for specified traffic and performance are derived along with numerical results. The degree of complexity and implementation alternatives for the various allocation schemes are considered.>